Container

ABSTRACT

A container for use in bulk transporting chemical goods, grains and the like, comprises a sack body in the form of a rectangular parallelepiped prepared from a cylindrical blown film. The container has a feeding end, a discharging end and a ventilating end. Enhanced pressure-resistive strength is obtained by improving the ventilating end-mounted design so as to have a specific shape. In one embodiment, a line slit is formed through the sack body, a cylindrical film is inserted into the slit, and the sack body and the cylindrical film are bonded to each other in line along the periphery of the slit so that the bonded corner spots, of the sack body and the cylindrical film, located at both ends of the slit, has a shape of a convex curve, for example, a circular shape or a ringed shape. This bonded structure makes it possible to deconcentrate pressure applied in using and filling the container without concentrating on the corner spot to prevent generation of pinholes and sack burst of the container.

CROSS REFERENCE TO RELATED APPLICATION

This application is the national phase application of InternationalApplication PCT/JP98/03804, filed Aug. 27, 1998.

FIELD OF THE INVENTION

The present invention relates to a plastic container for bulktransportation for use in safekeeping and transporting chemical goods,plastics, grains, fertilizers and the like, more especially to animproved container having a specific ventilator-mounted design.

BACKGROUND OF THE INVENTION

Bulk transportation of chemical goods, plastics, grains, fertilizers andthe like is practiced on a large scale now as a part of streamliningphysical distribution ways and means, and a large plastic container isused for one of the transportation means. For example, a sack in theform of a rectangular parallelepiped of 6 to 12 m in length made of acylindrical plastic film prepared by blown-film extrusion is actuallyused for transporting products stored therein.

Taking an example of this form by FIG. 1 showing a perspective view of acontainer, a container 1 is, as a whole, made of a sack body in the formof a rectangular parallelepiped prepared by cutting a cylindricalinflation film into the required length, folding both ends of the filmlongitudinally and bonding the superposed portion of the both ends. Thislarge container 1 is used for bulk transportation of, e.g., solidterephthalic acid. Terephthalic acid is introduced into the containerthrough a feeding end 3 by applying air pressure from outside.Terephthalic acid is taken out from a discharging end 4 to the outside.The facilitate filling and discharge the container has a ventilating end5 as an air passage.

Up to this time, this ventilating end has been mounted on the containerby making a short line slit through a sack body as for a body of acontainer, inserting a cylindrical film for a ventilating end into theslit and bonding both of them by heat-sealing.

Now, a process for mounting a ventilating end on a sack body will beexplained in more in detail with reference to FIGS. 10 and 11. FIG. 10is a perspective view showing the state of a ventilating end 100 mountedon a sack body 102, and FIG. 11 shows its cross-sectional view. Atfirst, as shown in FIG. 10, a sack body 102 is prepared by folding bothends of a film 101 and bonding the superposed portion 103 of the foldedends by heat-sealing. At this time, by inserting a cylindrical film 104into the superposed portion 103 and heat-sealing along the superposedportion 103, production of the sack body and mounting of the ventilatingend can be attained in one process. During this time, as shown in FIG.11, by inserting a fluorocarbon resin sheet 105 inside the cylindricalfilm 104, bonding both insides of the cylindrical film 104 to each otherduring heat-sealing can be avoided.

In this production process, a cone summit, or an acute summit isstructurally formed in both corners of the heat-sealed portion 106 ofthe sack body 102 and the cylindrical film 104. On condition that thesummit of the both corners is cone-shaped, stress due to air pressure instoring or discharging fillings concentrates on this spot to induce thegeneration of pinholes which start from the summit spot and extend alongthe heat-sealed portion 106. To this end, it has been hitherto takensuch measures as to prevent lowering of pressure produced by pinholes,easy which are easily developed in the vicinity of the heat-sealedportion 106 and bursting of the container with locally applied largestress, by applying a pressure-sensitive tape 107 for reinforcingclosely to (in the vicinity of) the heat-sealed portion 106.

However, these measures require much time taken in operation to resultin a raise of cost, and to enhance the adhesive strength of theheat-sealed portion still more is also needed.

DISCLOSURE OF THE INVENTION

Now, object of the invention is to enhance the pressure-resistivestrength of a container by improving the ventilating end-mounted designof a container. A second object of the present invention is to provide acontainer in the form of a sack from which generation of pinholes may beprevented without using a pressure-sensitive tape for reinforcing andbursting of a sack of a container may be prevented even when largestress is applied. These and other objects and advantages of theinvention may be readily ascertained by referring to the followingdescription and appended drawings.

Accordingly, the present invention provide to a container of a sack bodymade of plastic film through which a slit is made and a cylindrical filmis inserted therethrough, the sack body and the cylindrical film beingbonded to each other and united along the periphery of the slit, both ofthe bonded portions, of the sack body's periphery and the cylindricalfilm located around both ends of the slit along the longitudinaldirection, having a convex curve projecting toward the inside of thesack body. That both of the bonded portions have a circular or ringedshape is especially preferable for enhancing pressure-resistive strengthof the container.

In this container, since the corner spot where the sack body and thecylindrical film are bonded has a shape of convex curve projectingtoward the inside of the sack body, the pressure or stress applied tothe inside of the sack body may be made deconcentrated withoutconcentrating on the corner of the bonded portion. Accordingly,generation of pinholes can be suppressed, pressure-resistive strength ofthe container may be enhanced, and consequently, burst of the containermay be prevented.

The present invention also provide to a container in which a reinforcingfilm is bonded on the aforementioned bonded portion in the same shapewith that of the bonded portion. By this reinforcing film, pressure canbe deconcentrated as a matter of course, undercut from the bondedportion will be saved to prevent second cut, i.e. the bonded portionwill be kept the balance of thickness, and consequently, strength of thebonded portion may be increased still more.

The present invention further provide to a container of a sack bodyapproximately in the form of a rectangular parallelepiped, having at oneside portion of the sack body a feeding end for storing fillings intothe sack body by pressure, a discharging end for discharging thefillings out of the sack body and a ventilating end made of acylindrical film which is inserted into a slit made through the sackbody, the sack body and the cylindrical film being bonded to each otherand united, both of the bonded portions, of the sack body's peripheryand the cylindrical film located around opposite ends of the slit alongthe longitudinal direction, having a convex curve projecting toward theinside of the sack body. This container has high pressure-resistivestrength.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing a complete container, and

FIG. 2 is its top view.

FIG. 3 is a cross-sectional view for explaining an embodiment ofmounting a feeding end and a discharging end.

FIG. 4 is a perspective view of an essential part of a containerbelonging to one embodiment of the present invention.

FIG. 5 is a cross-sectional view for explaining a process for mounting aventilating end on a container.

FIGS. 6, 7 are each a perspective view regarding an essential part of acontainer belonging to other embodiments of the present invention.

FIG. 8 is a partially enlarged perspective view around a corner spotshown in FIG. 7.

FIG. 9 is a cross-sectional view regarding an essential part of acontainer belonging to other embodiment of the present invention.

FIG. 10 is a perspective view for explaining a conventional mountingdesign for a ventilating end on a container, and

FIG. 11 is its cross-sectional view.

THE BEST MODE FOR WORKING OF THE INVENTION

The constitution of a container according to the present invention willbe described in further detail by way of example with reference to theaccompanying drawings.

A container of the present invention is shown completely in aperspective view of FIG. 1, and its top view is shown in FIG. 2. Acontainer 1 for use in bulk transportation is of a sack body 2, which isapproximately in the form of a rectangular parallelepiped, and, on oneend portion of longitudinal direction, has a feeding end or feedingpassage 3 for use in feeding fillings by pressure from outside, adischarging end or discharge passage for use in discharging fillings outof the sack body, and further, a ventilating end or ventilator 5required in storing fillings through the feeding end 3 or dischargingfillings through the discharging end 4 by air pressure.

Materials of the container should not be limited, but a thermoplasticfilm or sheet is often used. For example, there can be used plastic filmincluding polyethylene such as low-density polyethylene (LDPE), linearlow-density polyethylene (LLDPE), ethylene-vinyl acetate copolymer(EVA.), polypropylene, nylon, polyethylene terephthalate (PET) or thelike, or otherwise, laminated film of these plastic film with otherthermoplastic film Appropriate material is selected depending on theproperty of substances to be filled into the container, fillingconditions and the like, and heat-resistant material is selected forhigh-temperature feeding; and gas barrier material is selected forfilling substances moisturized or oxidized. The film thickness may be 50to 400 μm, preferably 100 to 300 μm. When the film thickness is in thisrange, film is called "film" or "sheet" in general, but called "film"hereinafter in this specification.

The above feeding end 3 and discharging end 4 are mounted on the sackbody 2 in the same mounting process as suggested in FIG. 3. In thisprocess, approximately circular openings 8 and 9 are made through thepositions of the sack body 2 on which the feeding end 3 or thedischarging end 4 is to be mounted. Secondary, in such manner as toarrange outside cylindrical films, for finally providing feeding end 3and discharging end 4, i.e., cylindrical bodies 6 and 7, the opening 8(9) of the sack body 2 is covered with the cylindrical body 6 (7) whichis then superposed on the periphery of the opening 8 (9). Thereafter, anadhesive material 10 (11) is interposed between the cylindrical body 6(7) and the opening 8 (9) of the sack body 2, while a setting 12 (13) isput into the cylindrical body 6 (7). Then, the adhesive material 10 (11)is molten by heating and pressing with heat sealer 14 (15) from outside.Consequently, the cylindrical body 6 (7) is bonded to the sack body 2along the periphery of the opening 8 (9), thereby the feeding end 3 anddischarging end 4 are mounted on the sack body 2 in one piece. Here,when sack body and cylindrical body are made of melt-adhesive materialswhich make it possible to bond these bodies to each other, the adhesivematerial 10 (11), of course, may be eliminated.

For mounting ventilating end 5 on the sack body 2, which is one of theimprovement by the present invention, a different design from the designfor mounting the feeding end 3 and the discharging end 4 on the sackbody 2 is applied. FIG. 4 is a perspective view which suggests oneexample of the following mounting design. Namely, through a sack body 2made of plastic film , which is previously gusseted from diameterdirection of blown film toward center thereof, a slit 20 is made inline. Into the slit 20 a cylindrical film 21 for a ventilating end 5 isinserted, the sack body 2 and the cylindrical film 21 are bonded to eachother on the periphery 22 of the slit 20 to form a bonded portion 23.Then, the corner spot 23a, in the bonded portion 23, formed by bondingthe periphery 22a positioned at each end of slit 20 along itslongitudinal direction and the cylindrical film 21, is formed to have ashape of convex curve projecting toward the inside of the sack body 2,i.e., the direction of arrow line A as shown in FIG. 4. In other words,the corner spot 23a should have a shape of convex curve without formingan acute summit toward the inside of the sack body 2. As for thematerials of the sack body 2 and the cylindrical film 21, preferable arethose easy to melt and bond to each other, and especially, thermoplasticfilms of the same material are appropriately used because of havingtheir high adhesive strength. Of course, an adhesive layer may be formedbetween the sack body 2 and the cylindrical film 21 to enhance theiradhesive strength.

It is important for both of the corner spots 23a in the bonded portion23 of the sack body 2 and the cylindrical film 21 to have a shape curvedconvexity facing toward the inside of the sack body 2, and as a resultof the convex shape, a cone summit in the corner spot 23a isstructurally avoidable. Accordingly, even if stress concentration due toair pressure and the like is generated on both of corner spots 23a,stress on these areas will be deconcentrated, and accordingly, sackfailure or burst of the container 1 can be avoided. It is preferable forthe corner spot 23a to have usually a shape of circle, polygon havingnumber of angles not less than that of hexagon and resembling circle inshape or ring, and the circle may be round or ellipse. Otherwise, theshape may be semicircle or a shape of tongue as shown in FIG. 4.

Referring to FIG. 5, a process for mounting a ventilating end will beset forth in the following. At first, through a plastic sack body 2a aline slit 20 is made, and into the slit 20 a cylindrical film 21 of thesame material is inserted. Then, in order to avoid melt adhesion of thecylindrical film 21 between its facing insides, a fluorocarbon resinsheet 30 is inserted into the cylindrical film 21. Further, afluorocarbon resin sheet 32 is provided outside the cylindrical film 21.While maintaining this state, by heat-sealing in line from outside, sackbody 2 and cylindrical film 21 are at first melt-bonded along theperiphery 22 of a slit 20 to form a sealed line 26 and unify both ofthem. Secondary, with a circular heat sealer 31 the periphery 22a andthe cylindrical film 21, positioned at both ends of the slit 20 alongits longitudinal direction, are melt-bonded to each other while thefluorocarbon resin sheet 32 is sandwiched. This gives a container havingthe corner spot 23a curved convexity facing toward the inside of thesack body 2.

In this process, the circular heat sealer 31 has a diameter ranging fromabout 20 to 100 mm, preferably, from 40 to 60 mm, and its temperatureranges from 120 to 300° C., preferably from 200 to 250° C. This heatsealer may have a shape of circle, polygon, ring (doughnut) or the like.In case that the surface of the heat sealer is coated by fluorocarbonresin, adhesion to the film can be avoided, and accordingly, operationsbecome easy.

FIG. 6 is a perspective view showing other embodiment of the presentinvention. In this embodiment, film 25 for a sack body 2a is folded, acylindrical film 21 is inserted between the folded film, andheat-sealing is performed near a seam 27 in line. This results inmelt-bonding the film 25 and the cylindrical film 21 on a seal line 26as well as melt-bonding the film 25 mutually between its inner surfacesto form finally a sack body 2a.

Accordingly, in this embodiment, the seam 27 corresponds the slit 20 inFIG. 4. Further, in FIG. 6, the bonded portion 23a on the seal line 26,i.e., the superposed portion of the sack body 2a and the end 21a of thecylindrical film 21, corresponds to the corner spot 23a, as explained inreference to FIG. 4, and on this spot circular heat-sealing is performedto form a convex curve toward the inside of the sack body 2a.

FIG. 7 is a perspective view showing other embodiment of the presentinvention. In this embodiment, a film 25, which looks like two sheets offilm partially, is superposed on each other, a cylindrical film isinserted between the superposed portions of the film, and heat-sealingis performed near the superposed end 28 in line. This results inmelt-bonding the film 25 and the cylindrical film 21 on a seal line 26as well as the film 25 mutually between its inner faces to form a sackbody 2c. Accordingly, in this embodiment, the superposed end 28 area inwhich the film 25 is not mutually heat-sealed, i.e., the bonded portionof the film 25 and the cylindrical film 21 corresponds the slit 20 inFIG. 4. Further, as shown in FIG. 7, the bonded portion 23a on the sealline 26, i.e., the superposed portion of the sack body 2c and the end21a of the cylindrical film 21, corresponds to the corner spot 23a ashad explained in reference to FIG. 4, and on this spot ringedheat-sealing is performed to form a convex curve toward the inside ofthe sack body 2c.

Next, as to the corner spot heat-sealed in the ringed shape as shown inFIG. 7, more detailed explanation will be set forth. FIG. 8 is anenlarged perspective view around the corner spot 23a. In theconventional mounting process of a ventilating end, at an intersection("33" in FIG. 8), of the cylindrical film's end and seal line (whichcorresponds to a code "26" in FIG. 8) produced by heat-sealing a sackbody and a cylindrical film inserted into its slit in line, an acutesummit is inevitably formed so that inner stress concentrates on thispoint, and thereby bursting of container would occur in some cases. Incontrast, in the embodiment of the present invention as shown in FIG. 8,by forming a heat-sealed portion 23a, of ringed shape involving theaforementioned intersection, in the corner spot, an unbonded portion 23bof film 25 and cylindrical film 21 has a convex curve in outline, stresson the corner spot is deconcentrated, thereby the container may beprevented from bursting.

Another embodiment of the present invention is shown in FIG. 9 as across-sectional view. In this embodiment, on a corner spot 23a of a sackbody 2 and a cylindrical film 21, reinforcing films 24 of the samematerial are bonded in the same shape with that of the corner spot 23ain one piece. Namely, during the time of forming the corner spot 23a,the reinforcing films 24 are placed and superposed on the same place andheat-sealing is performed on the reinforcing films 24 to form a convexcurve toward the inside of the sack body 2, thereby forming the cornerspot 23a and bonding the reinforcing films 24 can be realized inparallel. In the FIG. 6, two sheets of tetragonal reinforcing film 24bonded on the corner spot 23 in one piece can be seen. In FIG. 7, twosheets of circular reinforcing film 24 sandwiching front and back film25 and bonded to the corner spot 23a on both side in one piece. In casethat the reinforcing film 24 is bonded on the corner spot 23a in onepiece in this way, strength of the corner spot 23a can be increased muchmore. Other constitutions may be the same as those in the embodiments ashad explained above.

EXAMPLE

In order to check the effect of the aforementioned container'sconstitutions, the embodiments of the present invention, followingexperiments were performed. Now, the present invention will be explainedmore in detail on the basis of the experimental results. However, it isto be understood that the invention is not intended to be limited to thespecific embodiments

Example 1

From the composition of low-density polyethylene (LDPE, melt flow rate(MFR)=0.5 g/10 min.; ASTM D1238) and ethylene-vinyl acetate copolymer(EVA, vinyl acetate content: 5 wt %) a cylindrical blown or inflationfilm of 200 μm in thickness was formed. By using this film, there wasprepared a container shown in FIG. 1 of a rectangular parallelepipedhaving length of about 5,900 mm, width of about 2,500 mm and height ofabout 2,400 mm. On this container feeding end 3 and discharging end 4were mounted, and further a ventilating end 5 was mounted in the samemanner as that explained in reference to FIG. 4.

Next, all the openings except that of the feeding end 3 were shut. Tothe feeding end 3 a gas blowing nozzle was connected, and further, ablower was connected to the nozzle. A manometer for measuring pressurein the container was mounted. While the blower was actuated to supplyair into the container, to the pressure in the container was increasedgradually, and the sealing state around the bonded portion 23 of theventilating end 5 was investigated. The result is reported in Table 1.

Example 2

By using the same film of Example 1, the same container of Example 1 wasprepared. The same procedure was repeated except that a ventilating end5a was mounted in the same manner as shown in FIG. 9. As to theresultant container sealing state around the bonded portion 23 of theventilating end 5a was investigated, and the result in Table 1.

Example 3

By using the same film of Example 1, the same container of Example 1 wasprepared. The same procedure was repeated except that a ventilating end5b was mounted in the same manner as shown in FIG. 6. As to theresultant container the sealing state around the bonded portion 23 ofthe ventilating end 5b was investigated, and the result is reported inTable 1.

Comparative Example 1

By using the same film of Example 1, the same container of Example 1 wasprepared. Then, a ventilating end 100 was mounted in the same manner asshown in FIG. 10, but adhesive sheet 107 as shown in FIG. 10 was notused. As to the container thus obtained in the same way as in Example 1sealing state around the bonded portion 23 of the ventilating end 5 wasinvestigated while the blower was actuated to supply air into thecontainer, to increase gradually the pressure in the container. Theresult in Table 1.

The results shown in Table 1 indicate that the containers of Example 1to 3 have improved pressure-resistive strength as compared with thecontainer of Comparative Example 1. Further, the containers of Example 2and 3 exhibit better results than that of Example 1. This suggests thatthe improving effect of the reinforcing film is considerably high.

                  TABLE 1                                                         ______________________________________                                        TEST RESULTS                                                                  ______________________________________                                        Example 1                                                                             The state of a sack body was observed while pressure                          was gradually increased and then 300 mmAq was                                 maintained for time. As a result, no change was                               observed. Even though pressure was further increased                          up to 500 mmAq, there was no pinhole generated and no                         change was observed.                                                  Example 2                                                                             The state of a sack body was observed while pressure was                      gradually increased and then 300 mmAq was maintained for                      a time. As a result, no change was observed. Even though                      pressure was further increased up to 500 mmAq, there                          was no pinhole generated and no change was observed.                          Moreover, there was no symptom of undercut from                               the bonded portion, and it was turn out that second                           cut was avoided.                                                      Example 3                                                                             Approximately the same result of Example 2 was obtained.                      Namely, no pinhole generated and no change was observed                       though pressure was increased up to 300 mmAq,                                 and there was no sympton of undercut from the bonded                          portion to prove that second cut was inhibited though                         pressure was increased up to 500 mmAq.                                Comparative                                                                           Pressure was gradually increased while the state of a sack            Example 1                                                                             body was observed. Generation of pinholes at the position                     structurally corresponding to a cone summit was started at                    100 mmAq. When pressure was further increased up to                           200 mmAq, pinholes was grown up to holes of 50 mm in                          diameter to fail practical value as a sack body.                      ______________________________________                                    

INDUSTRIAL APPLICABILITY OF THE INVENTION

According to the present invention, sack body and cylindrical film canbe bonded strongly, and this makes it possible to increasepressure-resistive strength of a container. Especially, the corner spotin the bonded portion of the sack body and the cylindrical body does notform acute summit as can be seen in the conventional container of a sackbody but forms a convex curve toward the inside of the sack body,thereby pressure applied inside the sack body does not concentrate onthe corner spot but can be deconcentrated, and accordingly, pinholegeneration of the bonded portion may be avoided to make it possible toenhance pressure-resistive strength as well as to prevent burst of thecontainer.

Further, when a reinforcing film is bonded to the corner spot whereinthe sack body and the cylindrical film are bonded to each other in thesame shape with that of the corner spot in one piece, stressdeconcentrates on the corner spot more surely, and undercut will besaved from the bonded portion, thereby second cut may become avoided. Bythis application of the reinforcing film, strength of the bonded portionof the sack body and the ventilator may be enhanced much more.

Moreover, in a container of the present invention, in preparing a sackbody from a film, a ventilating end can be mounted in parallel, and itis reduced or unnecessary to use a pressure-sensitive tape forreinforcing which has been used conventionally to enhance strength. Onthis account, effort and cost for preparing can be reduced.

It is further understood by those skilled in the art that the foregoingdescription is of preferred embodiments of the disclosed container andthat various changes and modifications may be made in the inventionwithout departing from the spirit and scope thereof.

What is claimed is:
 1. A container comprising a sack body made ofplastic film having a slit, said slit having opposed ends and peripheralside edges extending between the opposed ends, and a cylindrical filminserted through said slit, said sack body and said cylindrical filmbeing bonded to each other and united along the periphery of said slit,forming bonded portions, both of the bonded portions, of said slitperiphery and said cylindrical film located at both ends of said slitalong the longitudinal direction thereof, having a convex curveprojecting toward the inside of said sack body.
 2. The container asclaimed in claim 1, wherein said sack body is heat-sealed to saidcylindrical film.
 3. The container as claimed in claim 1, wherein saidslit comprises a linear cut in said sack body.
 4. The container asclaimed in claim 1, wherein said sack body is formed by folding a filmand sealing the resultant seam, and wherein said slit comprises anunsealed portion of said seam.
 5. The container as claimed in claim 1,wherein said slit comprises an unbonded portion formed in preparing saidsack body by superposing two sheets of film on each other and bondingthe superposed portion.
 6. The container as claimed in claim 1, whereineach of said bonded portions located around both ends of said slit alongthe longitudinal direction thereof, has a shape of circle.
 7. Thecontainer as claimed in claim 1, wherein each of said bonded portionslocated around both ends of said slit along the longitudinal directionthereof, has a shape of ring.
 8. A container comprising a sack body madeof plastic film having a slit, said slit having opposed ends andperipheral side edges extending between the opposing ends, and acylindrical film inserted through said slit, said sack body and saidcylindrical film being bonded to each other and united along theperipheral side edges of said slit forming bonded portions, both of thebonded portions, of said slit peripheral side edges and said cylindricalfilm located around both ends of said slit along the longitudinaldirection thereof, having a convex curve projecting toward the inside ofsaid sack body, and further comprising a reinforcing film having thesame shape as said bonded portions and being bonded thereon.
 9. Acontainer comprising a sack body having the approximate shape of arectangular parallelpiped, said sack body comprising at one end thereofa filling opening for introducing material to be stored in saidcontainer, a discharge opening for discharging material from saidcontainer, and a generally linear slit having opposed ends andperipheral side edges extending between said opposed ends, and aventilating end comprising a cylindrical film inserted into said sack,through said slit, said cylindrical film and said sack body being bondedto each other, in the vicinity of the peripheral side edges of saidslit, forming bonded portions, located around both of the opposed endsof the slit, along the longitudinal direction thereof, said bondedportions encompassing the ends of the slit, having a convex curveprojecting toward the inside of said sack body.